A methodological framework for reconstructing historical delta front morphology: case study at Macquarie rivulet delta within Lake Illawarra, Australia

摘要

Reconstructing past delta front morphology is a challenging task, due to complex morphological formation processes. We have developed a methodological framework to reconstruct the delta front morphology by integrating the information from historical shorelines, spatial distribution of depositional environments, relative sea-level changes and a modern Digital Elevation Model (DEM). The delta front morphology was reconstructed based on spatial connections between mud basin morphology, subaerial DEM and the historical shoreline. In addition, available sedimentation data at the delta front was utilized to aid in reflecting complex morphological formation processes. Taking Macquarie Rivulet delta within Lake IlIawarra, Australia, as an example, we generated the historical delta morphology for 1892. The modelled sedimentation rate appears to be consistent with the measured ones. We have also applied this method to reconstruct the historical morphology in 1938 and 1981. The model results indicate a progressive infilling influenced by switching river mouth locations. The cautions and implications of this method are also discussed. An increased resolution of sedimentation data should be able to improve the accuracy of the model. The reconstructed morphologies, elucidating fundamental information about delta evolution and sediment mass volumes in the past, can be employed in management activities.